Reversing valve for heat pumps



Marh -14, 1961 A. TRAsK REVERSI'NG VALVE FOR HEAT PUMPS Filed June 11.1959 .Fla-lv" FLOW RESTRICTING MEANS FIG.

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INVENTOR.

ALLEN TRASK y 1,914,682 REVRSING ,VALVE FOR HEAT PUMPS `Allen Trask,Utica, N.Y., or to international Heater This invention relates to heatpumpscomprising a re- 1 versible. compression type refrigeration systemand more particularly to the valve means for reversing the system. Acompression type heat pump used for cooling a residence or otherstructurein the summer and heating itV during thecolder mont-hsjofthejyear essentially comprises a reversible refrigeration Acircuitincluding an in door heat exchanger, an outdoor heat exchanger,Vcompressor means for effecting the flow of refrigerant through thecircuit, means for effecting and maintaining a pressure differentialbetween the two heat exchangers,

and a reversing valve means for. reversing the direction of refrigerantflow through the .heat exchangers.

A common type of refrigerant reversing valve is of the sliding typeknown as a D slide valve. 'Ihis type of valve has been in wide use insteam'enginee. The D slide is positioned on its seat in the position ofan inverted cup covering two of three ports. Ina heat'pump circuit the Dslide is held to its seatwith a pressure equal to the pressuredifference between the two heat exchangers.` When refrigerant Freon22",is used in the system, the pressure holding the D valve to its seatis in the order'of 200 pounds per square inch.

In damp weather of high humidity when outdoor temperatures range from25, F. to 40" F. the outdoor heat exchanger is operating at temperaturesbelow freezing most of the time. This causes frost and ice to accumulateon the outdoor heat exchanger to reduce its effectiveness. Whe'n theoutdoor heat exchanger is-the usual fin tube type, the tins accumulateice and frost between them blocking the iiow of air through them thusreducing their capacity for heat exchange. Means for frequent reversalof the system long ,enough to melt the accumulaf tions of frost and iceduring frost forming weather is usually provided in a heat pump. Suchdefrosting means is essential in heat vpumps operating 'in outdoortemperatures around 40 F. and lower.

Frequent reversingof a D slide type reversing valve operating under highpressurepresents aproblem of lubricatingthe valve seat. In compressiontype systems an amount of lubricating oil suihcient to lubricate thecorn-v pressor pistonsescapes 'from the compressor discharge valvesar'idcirculates around the refrigerant circuit with the refrigerant. Thislubricant is adequatein quantity to lubricate the D slide valve Vbutwhen the slide face and valve seat are both smooth and flat, as requiredto prevent refrigerant leaks, the valve pressure wipes the. lubricantfrom the valve seat in its normalsliding action. The pressure on the Dslide maintains such a tight contact between it and its seat thatlubricant cannot wet the valve face or itsvseat by capillary action toprovide for smooth lubricated movement of the D slide.

' A Vvalve forced to slide on a dry, nnlubricated seat is subject tosticking and abrasion which will cause tearing or galling of the valveface and/or the valve seat v and thereby cause the valve to leak.

A primary object of this invention is to posii suction side ofcompressor 3. vConduit 10 connects the p AIce tive lubrication in asliding type reversing'valve for .use

in heat pumps. Another object of this invention is to provide acombination of materials for a sliding type reversing valve wherein thevalve slide and/or its seat will entrain and A retain lubricant underall circumstances of heat pump functioning.

Another object of this invention is to provide a structure wherein theparts are subject to liberal tolerances The above and further objectsand advantages of thisv inventionwill become apparent from the followingdescription of the preferred embodiment thereof.

Referring to the drawings: Fig. l is a diagram of a conventional type ofreversible refrigeration system used for heat pumps;

Fig. 2 is a cross-sectional view of the reversing valve embodying thefeatures of the present invention; and Fig. 3 is a sectional view. takensubstantially on line 3 3 of Fig. 2. Referring to Fig. l, the heat pumpsystem shown diagrammatically comprises an indoor heat exchanger or coil1, andan outdoor heat exchanger or coil is usually larger than theindoor coil. f

Means for conducting refrigerant between ,the two heat exchanger coils,and reversing the direction of refrigerant flow, includes a compressor 3and a reversing valve 4. A pressure differential between the two coilsis maintained by a conventional type of refrigerant flow restrictingmeans 5. A three-way solenoid pilot valve 6 is connected by refrigerantconduits 7 and 8 to opposite ends of the reversing valve 4, and byconduit 9 to the discharge side of the compressor 3 to the reversingvalve 4. Conduit 11 connects the suction side of compressor 3 to thereversing valve 4.

Referring to Figs. 2 and 3, a D valve slide 12 has its lower surface orface 13 in contact with the flat seat 14 of the valve seat unit 19. Twopistons 15 in the cylindrical housing 16 are bolted by bolts 35 to theends of a yoke stamping 17 which also engages adjacent its center thevalve slide 12 by means of two upwardly extending cylindricalprojections 18 on the valve slide 12. Thus pistons 15, yoke 17,v andvalve slide 12 become a piston assembly.

'Ihe'valve seat unit 19 may be a casting or it may be moulded from analloy mixture of powdered metals, such as a mixture of powdered iron andpowdered copper, pressure moulded and sintered in a high temperaturefurnace having a reducing atmosphere. It is constructed with threedepending annular collars 20 spaced toA t three similarly spaced holes21 in thehousing 16, and is assembled into the housing with collars 20protruding a small amount below the outside of housing 16,

as shown in Figs. 2 and 3. Collars 20 have their inside diameters sizedto t three connecting tubes 11, 22 and 23.'

The valve seat unit 19 may be assembled and joined to the housing 16 andthe connecting tubes 11, 22 and 23 by silver soldering in one operationby applying the solder to the portion of annular'collars 20 extendingthrough to the outside of housing 16 and flowing the solder to cover theextended portion of collars 20, and making sweat solder joints betweenthe outside of the collars andv housing holes 2l, and between vtheinside of thehousing collars 20 and the ends of connecting tubes 11,

22 andz. A special featureof thisinveution is the Patented Mars 14, 1961l2, which construction which provides for the joining of these ve partsin one silver soldering operation.

Either one of two procedures may be used for the sequence of finishingthe flat valve seat 14 of valve seat unit 19 and assembling the unitinto the housing 16:

(l) The valve seat unit 19 may, in a first operation, be assembled bysilver soldering to housing 16 and tubes 11, 22 and 23; and in a secondoperation have its seat surface 14 finished fiat by a broachingoperation.

(2) The'valve seat unit 19 may, in a first operation, have its seatsurface 14 ground fiat in a surface grinding machine; and in a secondoperation it may be assembled by silver soldering to housing 16 andtubes 11, 22 and 23.

Either valve seat unit 19 or valve slide 12 may be made of a mouldedpowdered metal mixture compressed and sintered. The powder grain sizesshould be selected to result in the part having a microscopic spongelikeporosity providing capillary attraction and absorption of lubricatingoil customarily used for lubricating refrigeration compressors. Theporosity should be open enough to insure oil migration to its seatsurface, surface 13 for the valve slideand surface 14 for the valveseat, and tight enough to prevent blow-through of refrigerant gas underthe pressure differential range produced by the flow restricting means5.

Pistons are fit to cylindrical housing 16 with a comparatively loose fitto insure free piston movement within the manufacturing tolerances ofhousing 16 which may be seamless drawn steel tubing, and the piston asproduced on an automatic screw machine. Piston rings 24 are provided toassist in sealing the clearance between the pistons and housing 16.However, as pointed out hereinafter, this sealing is not complete andsome leakage around the piston is desirable.

A cylindrical recess 25 in the outer faces of the pistons 15 s providedwith a valve disc 26 held against a retaining ring 27 by a coil spring28. Cylinder heads 29 enclose the ends of cylindrical housing 16 towhich they may be silver soldered in assembly. A tubular part 30 havingvalve seat 31 at its inside end extends through each cylinder head 29 towhich it may be assembled by silver soldering, and is located so thateach valve seat 31 engages its respective valve disc 26 at each end ofthe piston assembly stroke. Pistons 15 are spaced apart by yoke 17 sothat at the end of each stroke one piston approaches valve seat unit 19as a stop, while the opposite piston brings its valve disc 26 to engageits valve seat 31, and move the valve disc from its retainer ring 27 bycompressing its valve spring 28 so that the valve disc rests freely onits seat.

Tubular parts 30 are closed at their outer ends while their bores are incommunication with conduits 7 and.8 respectively.

In the process of reversing the refrigerant flow, the solenoid pilotvalve 6 controls the operation of reversingvalve 4 in the followingmanner, well known to the art. When the piston assembly including the Dslide valve 12 is in its righthand position as shown in Fig. 2, thesolenoid pilot valve 6 provides communication between conduits 8, 9 and11 to the suction side of compressor 3, and closes-communication betweenconduits 7 and 9.

hand position, its valve disc 26 closes communication to conduit 8 byits seating on valve seat 31. Conduit 10 in communication with the highpressure side of compressor 3 conducts high pressure refrigerant vaporinto housing 16 between pistons 15. This vapor pressure leaks pastpiston rings 24 into cylinder head chambers 32 to equalize the pressureon both sides of both pistons 15. This restrained pressure equalizationis essential to the functioning of the reversing valve. Therefore theseamless steel tubing as it cornes from the tube mill is suitable forhousings 16 without internal machining. The normal out-of-round milltolerance will provide the required pressure leak past piston rings 24.

When the piston assembly and valve slide 12 is in the position shown inFig. 2, communication is established between outdoor heat exchanger 2and the suction side of compressor 3; indoor heat exchanger 1 is incommunication with the high pressure side of compressor 3; and thesystem is in the heating cycle.

When the system is to be reversed, solenoid pilot valve 6 is energizedto establish communication between conduits 7, 9 and 11 to the suctionside of compressor 3. The pressure in lefthand cylinder head chamber 32is quickly reduced to the compressor suction pressure, and the highpressure in righthand cylinder head chamber 32 expands to move thepiston assembly and valve slide 12 to the lefthand end of its strokewhere the valve disc 26 of lefthand piston 15 meets its seat 31 to closeit. DuringY the movement of the piston assembly from right to left, thepressure leakage past piston ring 24 of the righthand piston assists andaccelerates the movement. Thus leakage past the piston rings isdesirable.

When the piston assembly and slide valve 12 are in the lefthand positionopposite the position shown in Fig. 2, then communication is establishedbetween indoor heat exchanger 1 and the suction side of compressor 3;outdoor heat exchanger 2 is in communication with the high pressure sideof compressor 3; and the system is in the cooling cycle.

The closing of the conduits 7 and 8 by the valve discs 26 at the end ofthe left and righthand strokes respectively of the piston assemblyprevents the compressed refrigerant that might otherwise leak past oneor the other of the pistons, depending upon the left or righthandposition of the piston assembly, from passing through the then openpassageway of the pilot valve 6 to the suction side of the compressorwhich would thereby by-pass the heat exchangers.

In small sizes it may be desirable to produce valve seat unit 19 ofmoulded sintered metal powders, while in larger sizes it may be morepractical to make the valve seat of heat treated cast iron, and thevalve slide 12 of moulded sintered metal powders. In any size thestructure of this invention may be assembled of parts with a minimum ofmachining having customary dimensional tolerances of high quantityproduction in all operations.

'The only accuracy required is the atness and finish of the seating face13 of slide valve 12, and the valve seat 14 of valve seat unit 19. Bothof these parts may be surface ground and lapped to the required tiatnessand finish in high production machines. It is not required that adimensional tolerance be kept n these finishing operations.

-If it is desired to finish the fiat valve seat 14 of the valve seatunit 19 in a broaching operation, then this should be done after thesilver soldering operation wherein the housing 16, valve seat unit 19,and the three connecting tubes 11, 22 and 23 are assembled.

The piston and valve slide assembly will accept normal tube milltolerances for cold rolled mechanical seamless steel tubing. Thedistortions in cylindrical housing 16 which may be caused by the heat ofthe silver soldering operation can be tolerated because they will notrestrict when the righthand piston 15 is in its extreme rght vj ythefree movement of the piston assembly. If the housing is slightly bent,the bend will not cause the piston assembly to bind or stick. All thecomponents of the structure of this invention may be made in highproduction and assembled quickly with assurance of proper functioningafter a minimum of inspection.

While the invention has been shown and described in but a singlepreferred embodiment, it will be apparent that numerous modificationscan be made therein without departing from the spirit or essentialattributes thereof, and it is desired therefore that only suchlimitations be placed thereon as are imposed by the appended claims.

What is claimed is: 1. A refrigerant ow reversing valve for use in arefrigeration system comprising a cylindrical housing, a

'said annular collars extending through. the wall of said housing landbeing attached thereto and to said connecting tubes with solder, a Dvalve slide seating on said valve seat unit and arranged to selectivelyconnect each outside port with the center port,'and piston meansoperableby the pressures within said cylindrical housing for selectivelypositioning said D valve slide.

2. A refrigerant ow reversing valve for use in a refrigeration systemcomprising a cylindrical housing, a valve seat unit made of sinteredpowdered metal inside said housing having three ports andthree-individually associated annularcollars in communication withrespective ones of said ports, said sintered powdered metal having aporosity suitable to permit oil migration there through to the seatsurface and to prevent blow-through of the refrigerant gas used in thesystem, a reversing valve connecting tube ending inside each of saidcollars, said annular collars extending through the wall of said housingand being attached thereto and to said connecting tubes with solder, a Dvalve slide seating on said valve seat unit and arranged to selectivelyconnect each outside port with the center port, and piston meansoperable by the pressures within said cylindrical housing forselectively positioning said D valve slide. v

3. A refrigerant flow reversing valve for use in a refrigeration systemcomprising a cylindrical housing, a valve seat unit inside said housinghaving three ports and three individually associated annular collars incommunication witb respective ones of said ports, a reversing valveconnecting tube ending inside each of said collars, said annular collarsextending through the wall of said houssurface and to preventblow-through of the refrigerantgas used in the system, and piston meansoperable by the pressuresv within said cylindrical housing forselectively positioning said D valve slide.

4. A refrigerant ow reversing valve for use in a refrigeration systemcomprising a cylindrical housing,` a

valve seat unit inside said housing having three ports and A threeindividually associated annular collars in communication with respectiveones of said ports, a reversing valve connecting tube ending inside eachof said collars, said annular collars extending through the wall of saidhousing with solder, a D valve slideseating on said valve seat and beingattached thereto and to said connecting tubes unit and arranged toselectively connect eachv outside port with the center port, and pistonmeans operable by the pressures within s aid cylindrical housing forselectively positioning said D valve slide,'said'piston means includingtwo pistons fitting said cylindrical housing with one ofr each side ofsaid D valve slide connected together with a yoke engaging the valveslide.

References Cited in the tile of this patent UNITED STATES PATENTS261,485 Royce July 18, 1882 837,644 Reilly Dec. 4,v 1906 2,517,061 VonStackelberg- Aug. 1, 1950 -2,616,449 Maha Nov. 4, 1952 2,828,767 BaruschApr. 1, 1958 2,867,237 Allingham Jan. 6, 1959` 2,889,690 MacGrath June9, 1959

